KR20130124880A - Electroless copper plating bath and electroless copper plating method - Google Patents

Abstract

Provided are an electroless copper plating bath and an electroless copper plating method for enabling to use in neutral pH condition without formaldehyde, increasing the stability of the plating bath, and forming a plating film with proper thickness while electrodepositing a pattern only. In the present invention, the electroless copper plating bath in pH 4-9 contains water soluble copper salt, and amino boron or substituted derivatives thereof as a reducing agent, and also contains polyamino polyphosphonic acid, anionic surfactant, antimony compound, and nitrogen-containing aromatic compound as a complex agent. [Reference numerals] (AA) Deposition film thickness [關m/hrs];(BB) End part cutting generation;(CC) Antimony concentration [mg/L]

Description

Electroless Copper Plating Bath and Electroless Copper Plating Method {ELECTROLESS COPPER PLATING BATH AND ELECTROLESS COPPER PLATING METHOD}

The present invention relates to an electroless copper plating bath and an electroless copper plating method, and more particularly, to an electroless copper plating bath which does not contain formaldehyde and can be used in a neutral vicinity, and this electroless copper plating bath. It relates to the electroless copper plating method used. This application claims priority based on Japanese Patent Application No. 2012-105924 for which it applied on May 7, 2012 in Japan, and these applications are integrated in this application by reference.

In conventional electroless copper plating baths, formaldehyde is used as a reducing agent for copper ions, but formaldehyde has a high vapor pressure, deteriorates the working environment due to an irritating odor, and adverse effects on the human body due to carcinogenicity. . In addition, since the electroless copper plating bath using formaldehyde is strongly alkaline, it is easy to cause damage to the plated material and cause deterioration. For example, it cannot be effectively used for metals such as aluminum or aluminum alloy, Its use is limited.

On the other hand, for example, as described in Patent Document 1, an electroless copper plating bath using an amine borane or a derivative thereof is proposed without using formaldehyde as a reducing agent. This amine borane is a reducing agent which can be used in neutral to weak alkaline pH conditions, can prevent deterioration of the plated material and can be used with high safety.

However, this amine borane has a very high reducing power and has a problem of easily decomposing the plating bath. Up to now, there was no electroless copper plating bath solution having good bath stability and high practicality while containing this amine borane as a reducing agent.

In addition, when formaldehyde is used as a reducing agent, this formaldehyde selectively exhibits strong reducing properties with respect to metal surfaces such as palladium, copper, etc., while the reducing action in the plating bath is weak. Therefore, precipitation is performed at points other than the pattern (metal). (析出) was difficult to occur. In contrast, borane compounds such as dimethylamine borane have a strong reducing power enough to reduce water to hydrogen, and reduce the metal ions to metal not only on the metal but also in the plating bath. There was a problem of precipitation outside.

Japanese Patent Application Publication No. 2001-131761

Accordingly, the present invention has been made in view of the conventional situation as described above, and can be used in a pH condition near neutral without using formaldehyde, improves the stability of the plating bath, and also suppresses out-of-pattern precipitation. It is an object of the present invention to provide an electroless copper plating bath capable of forming a plated film having a good film thickness and an electroless copper plating method using the electroless copper plating bath.

MEANS TO SOLVE THE PROBLEM As a result of repeated examination in order to solve the above-mentioned object, in the formaldehyde free electroless copper plating bath, the pattern out precipitation is controlled by controlling the balance of the promotion action and the suppression action of plating precipitation. The present invention was completed to find that a plating film having a good film thickness can be effectively suppressed and a film thickness can be effectively formed.

That is, the electroless copper plating bath according to the present invention is an electroless copper plating bath having a water-soluble copper salt and an amino borane or a substituted derivative thereof as a reducing agent and containing no formaldehyde, and having a pH of 4-9 as a complexing agent. It is characterized by containing a polyamino polyphosphonic acid, an anionic surfactant, an antimony compound, and a nitrogen containing aromatic compound.

Moreover, the electroless copper plating method which concerns on this invention is characterized by forming a copper plating film with respect to a board | substrate using the said electroless copper plating bath.

According to the present invention, it can be used in a pH condition near neutral, and plating can be performed without damaging the plated object. In addition, plating precipitation outside the pattern can be effectively suppressed, and a plating film having a good film thickness can be formed. As a result, the plating process can be easily performed on a substrate such as aluminum or an aluminum alloy without providing a barrier layer or the like, and thus it can be suitably used for the manufacture of semiconductor wafers and the like.

1 is a graph showing the relationship between the antimony concentration and the deposited film thickness in an electroless copper plating bath.
2 is a graph showing the relationship between the antimony concentration and the deposited film thickness in the electroless copper plating bath.

EMBODIMENT OF THE INVENTION Hereinafter, specific embodiment (henceforth this embodiment) of an electroless copper plating bath and an electroless copper plating method which concern on this invention is described in detail according to the following procedures.

1. Electroless Copper Plating Bath

2. Electroless Copper Plating Method

3. Example

«1. Electroless Copper Plating Bath≫

The electroless copper plating bath according to the present embodiment is a so-called formaldehyde (formalin) -free plating bath containing no formaldehyde, which contains a water-soluble copper salt and aminoborane or a substituted derivative thereof as a reducing agent, and has a pH of 4 to 4. 9, electroless copper plating bath. The electroless copper plating bath is characterized by containing a polyamino polyphosphonic acid, an anionic surfactant, an antimony compound, and a nitrogen-containing aromatic compound as a complexing agent.

As described above, the electroless plating bath according to the present embodiment does not contain a reducing agent used under strong alkaline pH conditions such as formaldehyde and glyoxylic acid, and can be used in neutral to weak alkaline properties or aminoboranes thereof. Substituted derivatives are used as reducing agents. This prevents damage to the metal substrate to be plated, such as a strong alkaline plating bath using formaldehyde or the like as a reducing agent. Therefore, it can be used suitably as a plating bath for forming a plating film with respect to the semiconductor wafer which consists of aluminum, aluminum alloy, etc., for example, and can form a favorable plating film.

However, when aminoborane or a substituted derivative thereof is used as a reducing agent, the plating bath is easily decomposed due to a very strong reducing power, and there is a problem in that the pattern selectivity is low due to precipitation outside the pattern formed on the substrate to be plated. . However, in the electroless copper plating bath according to the present embodiment, the polyamino polyphosphonic acid, the anionic surfactant, the antimony compound, and the nitrogen-containing aromatic compound as the above-mentioned complexing agent are contained, thereby increasing the stability of the plating bath. It is possible to control the balance between the promoting action and the suppressing action of the plating precipitation, to form a plated film having high pattern selectivity and having a good film thickness.

According to such an electroless copper plating bath, for example, it is preferable that no barrier is formed on a metal substrate such as aluminum or an aluminum alloy or magnesium or magnesium alloy to prevent out-of-pattern deposition, without protruding. A plating film can be formed easily and can be used preferably, for example in manufacture of a semiconductor wafer.

<Aqueous copper salt>

Examples of the water-soluble copper salts include copper sulfate, copper nitrate, copper chloride, copper acetate, copper citric acid, copper tartarate, and copper gluconate. These water-soluble copper salts may be used alone or in combination of two or more thereof. It can be used by mixing in the ratio of.

As a concentration of water-soluble copper salt, copper concentration can be 0.005-0.5 mol / L, for example, it is preferable to set it as 0.01-0.5 mol / L, and it is more preferable to set it as 0.05-0.1 mol / L. If the concentration of the water-soluble copper salt is less than 0.005 mol / L, the deposition rate is slowed and the plating time becomes long, which is not economical. On the other hand, when the concentration exceeds 0.5 mol / L, the drag-out amount increases, the cost increases, and the plating liquid becomes unstable. In addition, nodule is generated or roughened, so that the patternability is lowered.

<Reduction agent>

Examples of the amine borane or substituted derivatives thereof as the reducing agent include dimethylamine borane, tert-butylamine borane, triethylamine borane, trimethylamine borane and the like.

An amine borane or its substituted derivative is a reducing agent which can be used from neutral to weak alkaline. Therefore, since it is not used in strong alkalinity, such as a plating bath using an aldehyde-based reducing agent such as formaldehyde or glyoxylic acid, damage to a metal substrate or the like to be plated can be suppressed and the deterioration can be prevented. . In addition, like an aldehyde-based reducing agent, it is possible to deteriorate the working environment or to exclude adverse effects on the human body, thereby improving safety.

It is preferable that the density | concentration of the amine borane or its substituted derivatives as a reducing agent shall be 0.01-0.5 mol / L.

<Complexing agent>

The electroless copper plating bath which concerns on this embodiment contains polyamino polyphosphonic acid as a complexing agent. Polyamino polyphosphonic acid is easy to complex copper ions efficiently in neutral vicinity, can suppress decomposition of a plating bath, and can improve stability.

Specifically, as this polyamino polyphosphonic acid, N, N, N ', N'- ethylenediamine tetrakis (methylene phosphonic acid), nitrile tris (methylene phosphonic acid), diethylenediamine penta (methylene, for example) Phosphonic acid), diethylene triamine penta (methylene phosphonic acid), bis (hexamethylene triamine penta (methylene phosphonic acid), glycine-N, N-bis (methylene phosphonic acid), etc. are mentioned.

Although the density | concentration of the polyamino polyphosphonic acid as a complexing agent is not specifically limited, It is preferable to set it as 0.01-1 mol / L. If the concentration is less than 0.01 mol / L, copper ions may not be sufficiently complexed and the plating bath may become unstable. On the other hand, when the concentration exceeds 1 mol / L, the drag-out amount increases, resulting in an increase in cost. In addition, since the deposition rate of copper becomes slow and the plating time becomes long, it is not economical. There is a possibility of damaging and deteriorating the base film.

<Anionic surfactant>

The electroless copper plating bath which concerns on this embodiment contains anionic surfactant. By containing an anionic surfactant, the stability of a plating bath can be improved.

The detailed mechanism for improving the stability of the plating bath is not clear, but by adding an anionic surfactant, the anionic surfactant is adsorbed to the metal fine particles generated in the plating bath, which further inhibits the growth of particles. It is considered that there is an effect of assisting dissolution of the fine particles by the above-mentioned complexing agent or other additives. In addition, it is considered that the stability of the bath is improved by inhibiting the aggregation and growth of the metal fine particles generated in the plating bath by the dispersing effect of the anionic surfactant.

On the other hand, in the cationic surfactant, the adsorption property of the metal fine particles to the surface is too high, thereby inhibiting the plating precipitation (the cationic surfactant adsorbed on the surface once becomes difficult to detach from the surface). In addition, nonionic surfactants have a lower adsorption property to metal fine particles and a weaker effect of improving bath stability than anionic surfactants and cationic surfactants. In addition, the electroless copper plating bath has a high salt concentration, whereby the non-ionic surfactant has a low cloud point and becomes cloudy easily. In addition, since a foaming property becomes strong when the nonionic surfactant is made to increase the density | concentration, it is difficult to raise concentration in order to improve bath stability.

Specifically, as the above-mentioned anionic surfactants, sodium salts of alkylcarboxylic acid-based surfactants and β-naphthalenesulfonic acid formalin condensates (for example, demol N manufactured by Gao Corporation, manufactured by Daiichi Pharmaceutical Co., Ltd.) Naphthalene sulfonate formaldehyde condensate, such as Laberin series, sodium polyoxyethylene lauryl ether sulfate (for example, Emar 20C manufactured by Gao Co., Ltd.) and polyoxyethylene alkyl ether sulfate triethanolamine [ For example, polyoxyalkylene ether sulfates such as Emar 20T manufactured by Gao Co., Ltd., sodium dodecyl sulfate (for example, Emar 10G manufactured by Gao Co., Ltd.) and dodecyl sulfate Higher alcohol sulfate esters such as triethanolamine [for example, Emar TD manufactured by Gao Corporation] and ammonium dodecyl sulfate [for example, Emar AD-25 manufactured by Gao Corporation] His Salt, sodium dodecylbenzenesulfonate [For example, Neopelex GS manufactured by Gao Corporation, Lipon LH-200 manufactured by Lion Corporation, Monogen Y manufactured by Daiichi Pharmaceutical Co., Ltd. Alkyl benzene sulfonic acid or salts thereof, such as -100), and straight chain alkylbenzene sulfonate (e.g., neogen S-20F manufactured by Daiichi Kogyo Co., Ltd.) [sodium dialkyl sulfosuccinate] , PEX OT-P manufactured by Gao Co., Ltd., Adekacol EC series manufactured by ADEKA Co., Ltd. or lauryl sulfosuccinate disodium [for example, Neo manufactured by Daiichi Pharmaceutical Co., Ltd.] Alkylsulfosuccinic acid ester-based surfactants such as hytenol LS and the like, sodium dioctylsulfosuccinate [for example, neo-Col SW-C manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.], polyoxyethylene alkylsulfosuccinic acid, or Salts thereof [for example, neohithenol S- produced by Daiichi Pharmaceutical Co., Ltd. 70), monoalkyl phosphate esters or salts thereof (e.g., Adecatol PS / CS / TS series manufactured by ADEKA Corporation, Phospanol series manufactured by Toho Chemical Industries, Ltd.), polyoxy Ethylene tridecyl ether phosphate esters (e.g., Flysurf A212C manufactured by Dai-ichi Pharmaceutical Co., Ltd.) and polyoxyethylene lauryl ether phosphate esters (e.g., manufactured by Dai-ichi Pharmaceutical Co., Ltd.) Polyoxyethylene alkyl ether phosphoric acid or its salt, α-olefinsulfonic acid or its salt [for example, neogen AO-90 etc. manufactured by Dai-ichi Pharmaceutical Co., Ltd.] etc. are mentioned, for example. Can be.

Although the density | concentration of an anionic surfactant is not specifically limited, It is preferable to set it as 0.01-2000 mg / L. If the concentration is less than 0.01 mg / L, the effect as a stabilizer cannot be sufficiently obtained, and the plating bath may become unstable. In addition, the nodule tends to be generated or roughened. On the other hand, when concentration exceeds 2000 mg / L, foamability becomes high too much. Moreover, the water washing property in a subsequent process falls and it becomes difficult for a waste liquid process and a drainage process.

<Antimony compound>

The electroless copper plating bath which concerns on this embodiment contains an antimony compound. By adding the antimony compound in this way, the precipitation rate is improved by the balance of the plating precipitation promoting effect by underpotential deposition phenomenon and the precipitation inhibiting effect by the catalytic poison effect due to the adsorption of antimony. Protrusion suppression effect can be obtained.

The underpotential precipitation phenomenon is the precipitation calculated theoretically because the precipitation of the target metal (copper) is promoted by the electrons released when the element (antimony) to be added is once redissolved as an ion immediately after reduction. It is the phenomenon that the metal precipitates at a potential lower than the potential.

Specifically, the antimony compound is convex upward when the effect of the concentration on the deposition rate of the plated metal is graphed, that is, the concentration at which the precipitation rate becomes slow even when the concentration is too low or too high and the precipitation rate becomes the maximum. Is present. Therefore, the inhibitory action is exhibited at the end portion of the pattern (edge portion) where antimony is easily adsorbed, and the promoting action is mainly exhibited at the end portion where the antimony is hardly adsorbed. It is believed to be present.

Here, the relationship between the deposition rate of the plated metal according to the concentration change of the antimony compound will be described in more detail with reference to specific experimental examples.

First, as Experimental Example 1, a pattern was formed by a TiN film on an Al-Si alloy sputter formed on a silicon wafer, and then a sample subjected to jincate treatment twice according to a prescribed method was shown below. The electroless copper plating process was performed by immersing in the electroless copper plating bath which consists of compositions for 1 hour, and the copper plating film was formed on the pattern.

[Electroless Copper Plating Bath Composition]

Ethylenediaminetetra (methylenephosphonic acid): 0.08 mol / L

Copper (copper sulfate, five hydrochloride): 0.063 mol / L (as copper concentration 4 g / L)

Dimethylamine borane ： 8 g / L

Sodium lauryl sulfate: 20 mg / L

o-phenanthroline: 4 mg / L

Antimony oxide: Refer to the following Table 1 (as antimony concentration)

pH ： 7.7

Bath temperature ： 60 degrees Celsius

And the film thickness of the formed plating film, the amount of precipitation out of a pattern (protrusion amount), and the external appearance of plating were investigated. Table 1 shows each measurement result. In addition, in FIG. 1, the change of the precipitation film thickness with respect to the antimony concentration in an electroless copper plating bath is shown. And in Table 1 below, "bridge" in protrusion evaluation shows the state in which patterns were connected by plating protrusion, and "end shaping generate | occur | produced" in external appearance evaluation is the film thickness of a board | substrate / pad outer peripheral part. Indicates that thinning occurs. And a protrusion value of minus means that plating does not precipitate in a pattern edge part by edge chipping, but the base part is exposed.

[Table 1]

When the plating treatment is performed under the plating bath composition and the conditions of the base portion in Experimental Example 1 described above, as shown in Table 1, in the case of no addition of antimony, a low concentration, and a high concentration, the plating deposition rate is slowed, and the plating film thickness is reduced. It turns out that it becomes thin and it turns out that precipitation abnormality in a pattern edge part arises. On the other hand, when antimony concentration is moderate in the density | concentration range of Table 1, it turns out that the plating film of a favorable film thickness is formed, and that the precipitation spreads out of a pattern and the edge clipping is suppressed.

Next, as Experimental Example 2, an electroless copper plating was performed by immersing a ceramic substrate patterned with a nickel film by palladium substitution treatment according to a regular method in an electroless plating bath having the same composition as Experimental Example 1 for 1 hour. The process was performed and the copper plating film was formed on the pattern. That is, the relationship between the precipitation rate of the plated metal according to the concentration change of the antimony compound was examined when the conditions of the base portion to be plated were changed. And the antimony oxide concentration (as antimony concentration) which is a component of a plating bath was changed as shown in following Table 2.

And the film thickness of the formed plating film, the amount of precipitation out of a pattern (protrusion amount), and plating appearance were investigated. Table 2 shows each measurement result. 2, the change of the precipitation film thickness with respect to the antimony concentration in an electroless copper plating bath is shown. In addition, the term for the evaluation in following Table 2 is the same as that of the said Table 1.

[Table 2]

As shown in Table 2, even when the conditions of the base portion were changed, in the case of no addition of antimony, low concentration, and high concentration, the plating precipitation rate was slowed, and the thickness of the plating film became thin, and more than the precipitation at the end of the pattern occurred. It can be seen that. On the other hand, when antimony concentration is moderate in the density | concentration range of Table 2, it turns out that the plating film of a favorable film thickness is formed, and the expansion of an out-of-pattern precipitation and chipping of an edge is suppressed.

As shown in Experimental Examples 1 and 2 as described above, the concentration range varies depending on the plating bath composition, the conditions of the plating base portion, the stirring conditions, and the like, but the precipitation rate is slow even when the concentration is too low, and the plating precipitation rate is maximized. It can be clearly seen that a tendency to be observed. In the concentration range in which the precipitation rate is maximum, the inhibitory action is exhibited at the pattern end (edge portion) where antimony is easily adsorbed, and the promotion action is mainly at the other end than where the antimony is hardly adsorbed. It is understood that it is possible to suppress the expansion (protrusion) of plating precipitation out of the pattern while forming a plating film having a thickness.

Therefore, by adding an antimony compound having a predetermined concentration to the plating bath in this manner, the deposition rate improvement and the protrusion suppression effect are obtained according to the balance between the plating precipitation promoting effect and the precipitation inhibiting effect due to the catalytic poisoning effect due to the adsorption of antimony to obtain the pattern selectivity. It is possible to form a plated film having a good film thickness in which the protrusion can be increased and the protrusion is suppressed.

The amount (concentration) of the specific antimony compound is different depending on the constituent components (plating composition) of the other plating bath, the conditions of the base portion, the stirring conditions, and the like, as described above. For example, it may be 0.1-20 mg / L, Preferably it is 0.5-10 mg / L, More preferably, it may be 1-4 mg / L.

It will not specifically limit, if it is a water-soluble compound melt | dissolved in a plating bath as an antimony compound, For example, antimony oxide, antimony chloride, etc. can be used.

<Nitrogen-containing aromatic compound>

The electroless copper plating bath which concerns on this embodiment contains a nitrogen containing aromatic compound.

Conventionally, nitrogen-containing aromatic compounds, such as 2,2'-bipyridyl and 1,10- phenanthroline, are used as a stabilizer of a plating bath, or a film physical property improving agent. However, although the detailed mechanism is not certain, by adding a nitrogen-containing aromatic compound to the electroless copper plating bath according to the present embodiment, the nitrogen-containing aromatic compound acts as an accelerator for promoting the plating metal.

Specifically, as the nitrogen-containing aromatic compound, imidazole or its substituted derivative, pyrazole or its substituted derivative, oxazole or its substituted derivative, thiazole or its substituted derivative, pyridine or its substituted derivative, pyrazine or its substituted derivative, Pyrimidine or substituted derivatives thereof, pyridazine or substituted derivatives thereof, triazine or substituted derivatives thereof, benzothiophene or substituted derivatives thereof, benzothiazole or substituted derivatives thereof, 2,2'-dipyridyl, 4,4 ' -Pyridine or substituted derivatives thereof, such as dipyridyl, nicotinic acid, nicotinamide, picolines, and lutidines; quinoline or substituted derivatives thereof, such as hydroxyquinoline, 3,6-dimethylaminoacridine, proflavin, and acrylamide; Acridine or substituted derivatives thereof, such as chrydinic acid and quinoline-1,2-dicarboxylic acid, uracil, uridine, thymine, 2-thiouracil, 6-methyl-2-thioura Pyrimidine or substituted derivatives thereof, such as sil, 6-propyl-2-thiouracil, phenanthroline or substituted derivatives thereof, such as 1,10-phenanthroline, neocouproin and vasophenanthroline, aminopurine, adenine And purine such as adenosine, guanine, hydantoin, adenosine, xanthine, hypoxanthine, caffeine, theophyrin, theobromine, aminopyrin, or substituted derivatives thereof.

Although the density | concentration of a nitrogen-containing aromatic compound is not specifically limited, It is preferable to set it as 0.01-1000 mg / L. If the concentration is less than 0.01 mg / L, the effect as an accelerator is not obtained, and the speed is slowed down, so that the plating time becomes long, which is not economical. In addition, precipitation of copper in the initial stage may deteriorate and damage to the base material may occur, or unprecipitated sites may occur. On the other hand, when the concentration exceeds 1000 mg / L, the precipitation rate is too fast, resulting in a crude coating. In addition, nodules tend to be generated or rough, and the patternability is lowered. In addition, there is a possibility that the plating bath becomes unstable.

<Other conditions>

The pH of the plating bath is set to pH 4.0 to 9.0, preferably pH 5.0 to 9.0, more preferably pH 6.0 to 8.0. As described above, the electroless copper plating bath according to the present embodiment contains an aminoborane or a substituted derivative thereof that can be used in neutral to alkaline conditions as a reducing agent. Thereby, it can be used in the range of pH 4.0-9.0, and can perform plating process, without damaging the base material to be plated.

Here, when the pH is less than 4.0, the natural consumption of the reducing agent increases, leading to an increase in cost, and the plating bath becomes unstable. On the other hand, when the pH is greater than 9.0, damage to the substrate to be plated becomes large.

PH of a plating bath can be adjusted by containing pH adjusters, such as sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide, for example.

Moreover, the temperature of a plating bath is although it does not specifically limit, It is 20-90 degreeC, Preferably it is 40-80 degreeC, More preferably, it is 60-70 degreeC. If the bath temperature is less than 20 ° C, the deposition rate is slow and the plating time becomes long, so it is not economical. On the other hand, when a bath temperature exceeds 90 degreeC, precipitation rate will become too high and it will be a rough film, and the base material may warp by heat shrink of the film after plating. Moreover, a nodule may generate | occur | produce or become rough, and pattern property may fall. In addition, the plating bath becomes unstable, and the natural consumption of the reducing agent increases, leading to an increase in cost.

As described above, in the electroless copper plating bath according to the present embodiment, in the electroless copper plating bath containing aminoborane or a substituted derivative thereof as a reducing agent and not containing formaldehyde, polyaminopolyphosphonic acid as a complexing agent , Anionic surfactant, antimony compound, and nitrogen-containing aromatic compound. According to this electroless copper plating bath, since it can be used in neutral vicinity, favorable plating process can be performed also to the to-be-plated object which does not damage to a to-be-plated object, for example, which is easy to deteriorate, such as aluminum.

In addition, according to the electroless copper plating bath, the stability of the plating bath can be improved, and the balance between the promoting action and the suppressing action of the plating deposition can be controlled, thereby effectively suppressing protruding out of the pattern, and on the other hand, It is possible to form a plated film having a desired film thickness as desired so that chipping or the like does not occur.

Thereby, for example, a good plating film without protruding can be easily formed on aluminum or aluminum alloy or magnesium or magnesium alloy without providing a barrier layer or the like for preventing out-of-pattern deposition. It can be used preferably at the time of manufacture of a semiconductor wafer.

In addition, as described above, since the balance between the promoting action of the plating precipitation and the suppressing action can be controlled, the plated film formed can be smoothed, for example, the peel strength of the wire bonding can be improved. Moreover, the appearance of this plating film is also very good.

«2. Electroless Copper Plating Method≫

Next, the electroless copper plating method using the electroless copper plating bath mentioned above is demonstrated. As the electroless plating method, a known method can be used. Moreover, a well-known method can also be applied to the catalyst provision process, when the catalyst provision process etc. are needed as pretreatment.

As mentioned above, the temperature at the time of electroless copper plating process controls the bath temperature of an electroless copper plating bath to 20-90 degreeC, Preferably it is 40-80 degreeC, More preferably, it is 60-70 degreeC.

In addition, the electroless copper plating process time is not specifically limited, What is necessary is just to set suitably so that it may become desired film thickness. Specifically, it can be made into about 30 second-15 hours, for example.

In addition, in performing the electroless copper plating treatment, as the plating treatment proceeds, copper ions are reduced to metal copper by the reducing agent and precipitated on the substrate, whereby the copper ion concentration and the reducing agent concentration in the plating liquid are lowered. pH will also change. Therefore, it is preferable to continuously or regularly supply the electrolytic copper plating solution with a water-soluble copper salt, a reducing agent, a complexing agent, and other additives as the copper ion source, and to maintain these concentrations in a constant concentration range.

Moreover, it is preferable to stir an electroless copper plating bath by methods, such as air bubbling, as needed.

Specifically, as the electroless copper plating method using the above-mentioned electroless copper plating bath, for example, without a barrier layer, the substrate is made of aluminum or an aluminum alloy, magnesium or a magnesium alloy. After the treatment, the electroless copper plating treatment is performed using the electroless copper plating bath described above. In the electroless copper plating method according to the present embodiment, since the out-of-pattern precipitation can be effectively suppressed as described above, a good plating film can be easily formed without providing a barrier layer or the like.

Alternatively, as another example of the electroless copper plating method, for example, copper, nickel, palladium, platinum, tungsten, molybdenum, rhodium, titanium, tantalum, or the like is replaced with palladium, platinum, copper, or the like to activate the thin film. After the treatment, the electroless copper plating treatment is performed using the electroless copper plating bath described above.

Alternatively, after the above-described active treatment, the reduction treatment is performed with a treatment liquid containing borane or a substituted derivative thereof, and then the electroless copper plating treatment is performed using the electroless copper plating bath described above.

[Example]

≪3. Example ''

Hereinafter, specific embodiments of the present invention will be described. In addition, this invention is not limited to any one of the following Examples.

<Review about the composition of the electroless copper plating bath>

First, in Examples 1 to 2 and Comparative Examples 1 to 10 shown below, the composition of the electroless plating bath was changed, and the film thickness of the plating film and the amount of precipitation out of the pattern (protrusion amount) were investigated. It was.

Example 1

(Electroless Copper Plating Bath Composition)

Ethylenediaminetetra (methylenephosphonic acid): 0.08 mol / L

Copper (copper sulfate, five hydrochloride): 0.063 mol / L (as copper concentration 4 g / L)

Dimethylamine borane ： 8 g / L

Sodium lauryl sulfate: 20 mg / L

o-phenanthroline: 4 mg / L

Antimony oxide: As antimony concentration, 2 mg / L

pH ： 7.7

Bath temperature ： 60 degrees Celsius

(Electroless Copper Plating Method)

After the pattern was formed on the Al-Si alloy sputter formed on the silicon wafer by a TiN film, the sample subjected to the quenching treatment twice in accordance with the conventional method was immersed in an electroless copper plating bath having the above-described composition for 1 hour. The electroless copper plating process was performed and the copper plating film was formed on the pattern.

(evaluation)

About the formed plating film, the plated film thickness was measured by the laser beam microscope by the height difference measurement before and behind a plating process. As a result, the formed plating film had a favorable film thickness of 5.3 micrometers and hardly protruded from the pattern to 5 micrometers.

[Example 2]

(Electroless Copper Plating Bath Composition)

Glycine-N, N-bis (methylenephosphonic acid): 0.13 mol / L

Copper (copper sulfate, five hydrochloride): 0.063 mol / L (as copper concentration 4 g / L)

Dimethylamine borane ： 8 g / L

Sodium lauryl sulfate: 20 mg / L

2,9-dimethyl-1,10-phenanthroline ： 2 mg / L

Antimony oxide: As antimony concentration, 2 mg / L

pH ： 7.7

Bath temperature ： 60 degrees Celsius

(Electroless Copper Plating Method)

After the pattern was formed on the Al-Si alloy sputter formed on the silicon wafer by a TiN film, the sample subjected to the quenching treatment twice according to the conventional method was immersed in an electroless copper plating bath having the above-described composition for 1 hour. The electroless copper plating process was performed and the copper plating film was formed on the pattern.

(evaluation)

About the formed plating film, the plated film thickness was measured by the laser beam microscope by the height difference measurement before and behind a plating process. As a result, the formed plating film had a favorable film thickness of 5.3 micrometers and hardly protruded from the pattern at 5 micrometers.

Comparative Example 1

The electroless copper plating treatment was performed in the same manner as in Example 1 except that the antimony compound was not added to the electroless copper plating bath composition to form a copper plating film on the pattern.

As a result, the film thickness of the formed plating film was 2.6 micrometers, compared with Examples 1 and 2, and the protrusion from the pattern was 15 micrometers or more. In this way, plating precipitation was suppressed, and a large amount of protruding precipitation occurred, resulting in a very low pattern selectivity.

Comparative Example 2

With respect to the electroless copper plating bath composition, except for adding 2 mg / L of lead instead of 2 mg / L of antimony, an electroless copper plating was performed in the same manner as in Example 1, and a copper plating film was formed on the pattern. Formed.

As a result, the film thickness of the formed plating film was 2.2 micrometers, compared with Examples 1 and 2, and the protrusion from the pattern was 12 micrometers. In this way, plating precipitation was suppressed, and a large amount of protruding precipitation occurred, resulting in a very low pattern selectivity.

[Comparative Example 3]

For the electroless copper plating bath composition, except that 0.3 mg / L of thallium was added instead of 2 mg / L of antimony, an electroless copper plating treatment was performed in the same manner as in Example 1, and the copper plating film was formed on the pattern. Formed.

As a result, the film thickness of the formed plating film was 1.8 µm, which was very thin in comparison with Examples 1 and 2. Moreover, since the amount of protrusion from the pattern was large, and the connection (bridge) between patterns was formed by this protrusion, the amount of protrusion could not be measured. In this way, plating precipitation was suppressed, and a large amount of protruding precipitation occurred, resulting in a very low pattern selectivity.

[Comparative Example 4]

The electroless copper plating treatment was performed in the same manner as in Example 1 except that sodium lauryl sulfate was not added to the electroless copper plating bath composition to form a copper plating film on the pattern.

In this Comparative Example 4, the plating bath was decomposed during the plating treatment, and the plating treatment could not be normally performed.

[Comparative Example 5]

The electroless copper plating treatment was performed in the same manner as in Example 1 except that no o-phenanthroline was added to the electroless copper plating bath composition to form a copper plating film on the pattern.

As a result, the protrusion from the pattern was as small as 0.5 占 퐉, but the plating film thickness was very thin as 1.2 占 퐉, and the plating rate was significantly lowered.

[Comparative Example 6]

The electroless copper plating treatment was carried out in the same manner as in Example 1, except that 0.5 g / L of polyethylene glycol (PEG) # 1000 was added instead of 20 mg / L of sodium lauryl sulfate in the electroless copper plating bath composition. The copper plating film was formed on the pattern.

In this Comparative Example 6, the plating bath was decomposed during the plating treatment, and the plating treatment could not be normally performed.

[Comparative Example 7]

The electroless copper plating treatment was performed in the same manner as in Example 1 except that bismuth 2 mg / L was added instead of antimony 2 mg / L to the electroless copper plating bath composition, and the copper plating film was formed on the pattern. Formed.

As a result, although the film thickness of the formed plating film was favorable at 4.4 micrometers, the connection (bridge) between patterns was formed by the protrusion of plating to the outside of a pattern, and the amount of protrusion was not able to be measured.

[Comparative Example 8]

Electroless copper plating was carried out in the same manner as in Example 1, except that 0.08 ml / L of diethylenetriamine pentaacetic acid was added instead of 0.08 mol / L of ethylenediaminetetra (methylenephosphonic acid) to the electroless copper plating bath composition. The process was performed and the copper plating film was formed on the pattern.

In this comparative example 8, copper plating did not precipitate, and the corrosion of the Al-Si alloy sputter which comprises the pattern generate | occur | produced.

[Comparative Example 9]

The electroless copper plating process was performed by the method similar to Example 1 except having used the electroless copper plating bath which consists of the following composition, and the copper plating film was formed on the pattern.

(Electroless Copper Plating Bath Composition)

Ethylenediaminetetraacetic acid ： 0.08 mol / L

Copper (copper sulfate, five hydrochloride): 0.0315 mol / L (as copper concentration 2 g / L)

Formaldehyde ： 2 g / L

Polyethylene glycol (PEG) ＃ 1000: 1 g / L

2,2 "-dipyridyl: 20 mg / L

pH: 13.2 (adjust with NaOH)

Bath temperature ： 60 degrees Celsius

In Comparative Example 9, the Al-Si alloy sputter was dissolved and plating could not be performed normally. This is considered to be because the plating bath uses formaldehyde as a reducing agent and is highly alkaline, thus causing damage to the substrate.

[Comparative Example 10]

The electroless copper plating process was performed by the method similar to Example 1 except having used the electroless copper plating bath which consists of the following composition, and the copper plating film was formed on the pattern.

(Electroless Copper Plating Bath Composition)

Ethylenediaminetetraacetic acid ： 0.08 mol / L

Copper (copper sulfate, five hydrochloride): 0.0315 mol / L (as copper concentration 2 g / L)

Glyoxylic acid ： 6 g / L

Polyethylene glycol (PEG) ＃ 1000: 1 g / L

2,2 "-dipyridyl: 20 mg / L

pH: 13.2 (adjust with NaOH)

Bath temperature ： 60 degrees Celsius

In this Comparative Example 10, the Al-Si alloy sputter was dissolved and plating could not be performed normally. This is considered to be because the plating bath uses glyoxylic acid as the reducing agent and is highly alkaline like formaldehyde, and thus damage to the substrate is increased.

Claims (7)

As an electroless copper plating bath of pH 4-9 which contains a water-soluble copper salt and aminoborane or its substituted derivative as a reducing agent, and does not contain formaldehyde,
Polyaminopolyphosphonic acid as complexing agent;
Anionic surfactants;
Antimony compounds; And
Nitrogen-containing aromatic compounds
Electroless copper plating bath containing a. The method of claim 1,
The electroless copper plating bath whose density | concentration of the said polyamino polyphosphonic acid is 0.01-1 mol / L. The method of claim 1,
The electroless copper plating bath whose density | concentration of the said anionic surfactant is 0.01-2000 mg / L. The method of claim 1,
The electroless copper plating bath whose density | concentration of the said antimony compound is 0.1-20 mg / L. The method of claim 1,
The electroless copper plating bath whose density | concentration of the said nitrogen-containing aromatic compound is 0.01-1000 mg / L. The electroless copper plating method which forms a copper plating film with respect to a base material using the electroless copper plating bath of Claim 1. The method according to claim 6,
The base material is aluminum or an aluminum alloy, or magnesium or magnesium alloy, electroless copper plating method.

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